Electric heating unit.



HIE. FRICKEY.

ELECTRIC HEATING UNIT.

APPLICATION FILED FEB. 26. 1916.

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v UNITED STATES PATENT. OFFICE.

ROYAL n: rnrcKEY, ,or nnnnme, CALIFORNIA.

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To all whommay concern:

Be it known that I, RoYAL E. Fnionnv, a citizen of the United States, and a resldent of Bedding, Shasta county, State of California, have invented a certain new and use fulElectric Heating Unit, of which the following is a specification. The invention relates to-devices which are adapted to be submerged. in thewater or other liquid to be heated.

An object of the invention is to provide a heating unit having a low temperature gradient between the heating element and the fluid to be heated, and'also to provide a heating element which is protected from oxidation.

Another object of'the invention is to provide a submersible electric heating unit comprising a unltary structure.

Another object of the invention is to provide means within the heating unit for automatically opening the. electric circuit when the temperature therein reaches a certainpredetermined maximum..

The inventlon; possesses other advanta-- geous features, some ofwhich, with the foregoing, will be set forth at length in the fol lowing description, where I shall outline in full that form of the invention which I have selected for illustration inthe drawings accompanying and forming part of the present specification. In said drawings I have shown one specific form of my invention, but

it is to beunderstood that I do not limit myself to such form, since the invention scale taken on the line Fig. 1.

Fig. 4 is a crosssection on an enlarged scale taken on the line 44 Fig. 1.

The heater of my invention comprises a unitary structure which may be readily applied to any tank or receptacle, the h uid content whereof it is desirable to heat. e heater comprises a sealed metallic container or tube 2 provided on its end with a r'educ Specification of Letters Patent.

Patented Aug. 28, 1917.

Application filed February 26, 191I Serial No. 80,622.

tion nipple 3 and an integral nut 4 for screwing thetube to a firm seat in a tapped boss 5 in the Wall 69f a tank or other receptacle. Screwed tightlywinto the-nipple 3 and closing the outer end of the tube is a along its edges in which the successive convolutions of the heating coil are embedded. The insulator is but slightly narrower in width than the internal diameter of the tube 2, so that it acts to center the heating coil in the tube. By forming the heating element of fiat thin wire, a much greater area of surface is obtained than with around wire of the same cross section. The lower end of the insulator 10 is secured in a slot in the plug 7 and attached to the upper end is a guard or spacer 12 which contacts'with the tube, holding the heating coilcentrally and out of contact with the tube. The upper end of the heating coil is connected to a substantially stifl metallic bar or stri 13 which extends downward through the insulation strip 10 and serves as a support therefor when micaor other flexible material is employed for the insulator 10, and also con stitutes the electric conductor. 1 The con-. ductor 13 is offset at.its lower end and is rigidly connected to a boss formed on the end of thefeed conductor '14:. The'lower joint therewith. The metallic plug 7 is pro:-

vided with a flange 17 for the engagement of a wrench and when screwed into place the flangebears against the nut 4. Secured to the plug 7 and bearing against the flange 17 is a cap 18 through which the conductors 14.15' pass, the conductors being suitably insulated.

Heretoforeheating elements which have been inclosed in metallic tubes have usually been wrap'ped'with' mica or other comparable insulatin material, to insulate, them from the ine osing tube, but the electrical insulating material is also an eflicient heat insulator, resulting in a steep temsubstance which is fluid at the temperature of operation of the heater. The material which I prefer to employ is oil of the proper characteristics, but the use of oil is not essential and any other suitable substance may be employed. By employing such medium, which is in direct contact with the heating wires and with the walls of the tube, the

heat is conveyed to the tube by convection.

with a low temperature drop between the heating element and the tube. Suflicient of the fluid material is placed in the tube to submerge the heatin element, thereby protecting it from oxidation, and the tube is preferably only partially filled to allow an air space so that increase in volume due to increase in temperature will not materially increase the pressure Within the tube. I Since the heat is rapidly transferred from the heating element to the tube by convection and on account of-the large surface of -the heating elementin contact with thefluid, there is a small temperature drop between the maximum temperature at the heating element and the minimum temperature at the tube.

The heatingunit is preferably arranged 'inthe tank containing the liquid to be heat-.

ed, in a vertical po'sition,-but it may be employed in any desired position.

Means are also provided for automatically wound on said stri opening the electric circuit should the temperature within the tube exceed a certain predetermined maximum. Arranged in the electric circuit within the tube and preferably at the upper end thereof, is a metallic fuse 19 which melts at the predetermined temperature. This fuse ispreferably interposed between the wire 9 and the supporting conductor 13. When destroyed, this fuse maybe renewed by removing the plug and the heating element from the tube.

I claim:

1. An electric heating unit comprising a sealed tube, a plug closing the lower end of said tube, a strip of insulating material mounted on said plug and provided with indentations along its edges, a resistance wire dentations and a fil ing of fluid electric insulating material in said tube.

2. An electric heating unit comprising a.

sealed tube, an electric heating element in said tube, a circuit for the heating element, a fuse in said circuit and tube adapted to be melted by the increase in temperature in the tube to a certain predetermined degree and a filling vof fluid sulating material in which said element is s.- .merged.

In testimony whereof, I have hereunto set my hand at" Redding, California, this 18th day of February 191 ROYAL E. FRICKEY.

In presence of HENRY G. ANNA A. BROWN.

and seated in said in 

